Mechanical-electrical transducer



Oct. 1970 I P. L. D. HUMBERT-DROZ 3,536,932

MECHANICAL-ELECTRICAL TRANSDUCER Y Filed April 10, 1969 PATRICE L. D. HUMBERT-DROZ United States Patent 3,536,932 MECHANICAL-ELECTRICAL TRANSDUCER Patrice Louis David Humbert-Droz, Ottawa, Ontario,

Canada, assignor to Northern Electric Company Limited, Montreal, Quebec, Canada Filed Apr. 10, 1969, Ser. No. 815,064 Int. Cl. H01f 21/06 US. Cl. 307-106 14 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to the mechanical-electrical transduction of energy using fluid pressure and more particularly to a fluid pressure switching matrix and switch.

In push-button telephone dials using tone dialling, each dialled number, selected by pushing a dial button, is converted into two different electrical impulses which are identified by the station apparatus to which the telephone is connected. The modulating impulse which identifies the selected number has been produced by an electronic circuit derived by a plurality of spring contacts. Certain disadvantages arise from this type of mechanical system, such as the problem backlash which is expensive to reduce, the low reliability of the spring contacts, and the brief duration of the modulating impulse cornpared with the push button contact time, which reduces the reliability of identification of the signal.

It is an object of the present invention to provide a switching matrix employing fluid pressure to convert mechanical energy, imparted to a key or push button, into 1 electrical signals identifying the particular button which is pushed.

Another object of the invention is to provide an xy encoding system of digital signalling using a mechanicalhydraulic-electrical transduction of energy.

Another object of the invention is to provide an improved electrical switch employing fluid pressure to convert mechanical pressure into an electrical signal.

An example embodiment of the invention is shown in the accompanying drawings in which:

FIG. 1 is a view in perspective, partly schematic, of a push-button array and its associated fluid pressure conversion elements;

FIG. 2 is a view in perspective of a portion of the housing and push-button array of FIG. 1, partly broken away (and viewed from the side opposite that presented in FIG. 1), showing the arrangement of the tubes within the housing and the manner in which each key interacts with the tubes.

FIG. 3 is a view in perspective, partly broken away, showing the inter-relationship between each tube and a magnetic circuit; and

FIG. 4 is a view similar to FIG. 3 showing the movement of fluid in the tube, in relation to the magnetic circuit, when the tube is compressed by its associated pushbutton.

" and columns. Each button 12 is loosely retained in an aperture 13 in dial plate 11 and projects both above and below the dial plate, the upper projecting portion carrying indicia.

Underlying dial plate 11 and within housing 10* are two groups of spaced apart tubes 14 in parallel planes, forming a grid with crosspoints of the tubes lying directly beneath buttons 12. Thus a plurality of parallel row tubes 14a and a plurality of column tubes 14b are provided, corresponding to the rows and columns of buttons 12.

To arrange tubes 14 in this manner, a plurality of channels 15 are located in housing 10 to form a grid corresponding to that formed by tubes 14. As seen in the drawings, channels 15a accommodating row tubes 14a are shallower than channels 15b accommodating column tubes 14b, the difference in depth being equivalent at least to the sum of the diameter of tube 14b, the thickness of a pressure lip on button 12 (to be described) and the thickness of a bridging strip 16 which interconnects separated portions of the trough of each channel 15a. Bridging strip 16 is slightly longer than the width of channel 15b and rests at each of its ends on a ledge 17 cut out of the end of adjacent portions of channel 15a.

To provide contact with both tube 14a and tube 14b simultaneously at their intersections, each button 12 is formed with a rectangular recess 18 in the shaft of the button lying below dial plate 11. Recess 18 accommodates tube 14a and strip 16, its width from upper wall 19 to lower wall 20 being at least the sum of the diameter of tube 14a and the thickness of interconnecting strip 16. Recess 18 provides a lower lip 21 for the shaft of button 12 which is accommodated between strip 16 and tube 14b,

and touches tube 14b when face 19 of recess 18 touches tube 14a. Each button 12 may of course be urged upwardly by spring means, not shown, urging lip 21 against strip 16. i

As seen in FIG. 1 of the drawings, one end 22 of each tube 14 is sealed while the other end of each tube extends out from the housing and terminates in a sealed end portion or extension 23 of constricted diameter. Tube 14, including constriction 23, is filled with a non-compressible ferromagnetic liquid 24 with a compressible cushion of gas 25 separating liquid 24 from the sealed end .of constriction 23, as shown more particularly in FIG. 3 of the drawings. That portion of constriction 23 holding gas cushion 25 is located within a gap 26 of a continuous permanent magnet 27 which has coupled with it an output coil or winding 28 forming part of an electrical circuit (not shown) in which an electrical signal may be induced. Meniscus 29 of liquid 24 in constriction 23 lies adjacent gap 26, the proportions of tube 14, constriction 23 and gas cushion 25 being such that on compression of the tube by button 12, meniscus 29 will pass through gap 26 of magnet 27 to cut across a maximum number of flux lines of force in the magnetic field provided by magnet 27. For this reason the sealed end portion of constriction 23 will lie outside gap 26 to accommodate gas cushion 25 in a compressed state, as shown in FIG. 4 of the drawings. As will be seen in FIG. 1, each tube 14 has an individual magnet 26 associated with it together with an individual coil 27 and electrical circuit in which a signal is induced. Of course magnets 27 may be arranged in any suitable manner in relation to housing and tubes 14 may be coupled with constrictions 23 in any suitable manner to carry the operation of the device into effect.

It will be seen that pairs of magnets 27 and their associated coils 28 serve to identity, through tubes 14, individual crosspoints and push-buttons 12, different combinations of magnets identifying different crosspoints, thus froming an xy encoding system.

The ferromagnetic fluid used in tubes 14 is preferably a colloidal suspension of submicron-sized ferrite particles in a carrier fluid, with a dispersing agent added to prevent flocculation. The suitable fluid is made up as follows:

Particles size--100 A.

Particles concentration10 per cm. Carrier fluidkerosene Dispersing agentoleic acid This fluid has a magnetic permeability of 1,113 and a magnetic induction greater than 70 gauss.

Tubes 14 may be formed of any suitable resilient ma terial such as a rubber compound, which will retain fluid 24 and the gas of cushion without deterioration.

In the opeartion of the described embodiment, any button 12 when pushed downward in the direction of arrow will bear simultaneously against the crosspoints of two tubes 14a and 14b where they intersect the axis of the button, face 19 of recess 18 pressing against tube 14a and lip 21 pressing against tube 14b to compress each tube. The force imparted by button 12 to compress each tube 14 displaces non-compressible fluid 24 in that tube, which acts against compressible gas cushion 25, causing the fluid to move across gap 26 of magnet 27 as the gas in compressed by the force transposed by the fluid from the button, as shown by arrow 31 in FIG. 4 of the drawings. The movement of ferromagnetic fluid 24 through gap 26 will vary the reluctance of the magnetic circuit in magnet 27 to produce an electromotive force in output coil 28. Since the electromotive force generated in coil 28 is proportional to the change in reluctance of the magnetic circuit and hence to the rate of movement of fluid 24 through gap 26 of permanent magnet 27, constriction of tube 14 in that portion of the tube lying within the gap increases the rate of movement of the fluid and hence the strength of the signal induced into the electrical circuit of coil 28.

As mentioned above, coil 28 forms part of an electrical circuit (not shown) which carries the signal, induced in the coil by magnet 27, by suitable circuitry (normally an amplifying circuit and a delay circuit) to an oscillator. A pair of such signals, induced by a pair of magnets 27 identifying a particular push-button 12, generates a tone signal in the oscillator identifying the digitally selected number.

It will be appreciated that the magnetic field, to which the electrical circuit is coupled, may be produced electromagnetically by providing an exciting current in coil 28 or in a separate coil using a core equivalent to magnet 27. If desired, extension 23 could be used as the core of a solenoid acting both as a magnetizing coil and as a signal output coil. Again, the hydraulic pressure exerted by any non-compressible fluid 24, not necessarily ferromagnetic, could be exerted on a solid piston of ferromagnetic material located within constriction 23 and movable into gap 26 of magnet 27 (or into a solenoid) with a cushion of gas 25 being present for compressibility and to return the piston to its original position of rest when pressure on button 12 is released.

I claim:

1. A mechanical-electrical energy transducer comprismg:

at least two groups of flexible, closed tubes disposed in contiguous planes, with the longitudinal axes of the tubes of one group crossing those of the other group to form a grid, each of the tubes carrying a noncompressible fluid therein;

means responsive to a change of pressure of the fluid in each of the tubes to produce, for each tube, an electrical signal; and

actuating means located adjacent the tubes at each crosspoint thereof selectively adapted to compress the tubes adjacent thereto whereby the pressure responsive means is actuated.

2. A transducer as claimed in claim 1 in which at least a portion of each tube is located in an individual magnetic field and an individual electrical circuit is coupled with each magnetic field, the fluid in each tube being adapted to be displaced on compression of the tube to move magnetically conducting material across the field whereby a signal is induced in the electrical circuit.

3. A transducer as claimed in claim 2 in which a permanent magnet, having an air gap therein, provides a closed magnetic circuit, the tube portion being located in the air gap, and the electrical circuit having a winding on the magnet.

4. A transducer as claimed in claim 2 including a ferromagnetic core having an air gap therein, the electrical circuit having a first winding on the core, the tube portion being located in the air gap, and a second winding of a further electrical circuit providing an exciting current to produce a magnetic circuit in the core.

5. A transducer as claimed in claim 2 in which a ferromagnetic core, having an air gap therein, carries a winding of said electrical circuit providing an exciting current to produce a magnetic circuit in the core, the tube portion being located in the air gap.

6. A transducer as claimed in claim 2 in which the magnetic field is produced by a solenoid in the electrical circuit, the tube portion constituting the solenoid core.

7. A transducer as claimed in claim 2 in which the magnetically conducting material is ferromagnetic fluid, and a compressible fluid contained in the tube discrete from the ferromagnetic fluid whereby the ferromagnetic fluid is movable longitudinally in the tube across the magnetic field.

8. A transducer as claimed in claim 2 in which one end portion of the tube lies in the magnetic field, said end portion comprising an extension of restricted diameter.

9. An xy encoding device comprising:

a housing;

two groups of transversely flexible, closed tubes disposed in contiguous planes to form a grid in the housing, each of the tubes carrying ferromagnetic fluid therein;

one end portion of each tube terminating in an individual magnetic field having an electrical circuit coupled therewith, said tube end portion carrying a discrete compressible fluid;

a shaft located at each crosspoint of the tubes transversely thereto and projecting from the housing, each shaft being constructed and arranged, on an axial force being applied thereto, to compress the pair of tubes at the crosspoint, the displaced fluid in each of said pair of tubes moving along the tube and across the magnetic field to induce a signal in the electrical circuit, the two signals induced by said tubes identifying said crosspoint.

10. A device as claimed in claim 9 in which each of said tube end portions lies in an air gap of a permanent magnet providing a closed magnetic circuit, the electrical circuit having a series winding on said magnet.

11. A device as claimed in claim 9 in which each of said tube end portions lies in an air gap of an electromagnet providing a closed magnetic circuit, the electrical circuit having a series winding on the electromagnet and supplying the exciting current therefor.

12. A device as claimed in claim 9 in which each of References Cited said tube end portions lies in the Core Of a solenoid in UNITED STATES PATENTS series w1th the electncal circuit, theexc tmg current for 2,120,048 6/1938 Turner X said soleno1d bemg supplied by said circuit. 3,080,720 3/1963 Downs et a1 200*815 X 13. A device as claimed in claim '9 in which the end 5 3,260,819 7/1966 Swim) at a] portion of each tube terminating in the magnetic field is 3,441 743 4 1959 Carroll 3 7 1 X reduced in diameter to provide a constricted extension f the tube ROBERT K. SCHAEFER, Primary Examiner 14. A device as claimed in claim 13 in which the dis- 10 T. B. JOIKE, Assistant Examiner crete compressible fluid is located in the extension of the tube contiguous with the colsed end thereof and with but outside the magnetic field. 3351, 237; 33630, 134; 340166 

